Optical information reproduction apparatus

Abstract

An optical information reproduction apparatus has a section which scans with an optical beam an optical information recording medium in which information is recorded. The optical beam is modulated according to the information. From this modulated optical beam, the corresponding reproduction signal is generated, then binary-converted. A sampling clock synchronized with this binary-converted reproduction signal is generated. The binary-converted reproduction signal is sampled with the synchronized sampling clock to reproduce the information. The response of the sampling-clock generating section can be switched. This optical information reproduction apparatus enables reliable information reproduction.

What is claimed is: 
     
       1. An apparatus for reproducing information from an optical information recording medium comprising an area for recording a phase-locked-loop synchronizing signal and an area for recording data, and a specific signal recorded between the two areas, said apparatus comprising: means for generating a reproduction signal by scanning the recording medium with an optical beam;   a specific-signal detector for detecting the specific signal from the reproduction signal;   a binary-conversion circuit for converting the reproduction signal to a binary signal;   a sampling-clock generating circuit for generating a sampling clock, synchronized with the binary reproduction signal; and   a reproduction circuit for reproducing information by sampling the binary reproduction signal with the sampling clock,   wherein said sampling-clock generating circuit comprises (i) a phase comparator for generating a phase-comparing signal by comparing a phase of the binary reproduction signal with that of the sampling clock, (ii) a low-pass filter comprising an amplifier into which the phase-comparing signal is inputted through two resistors which are connected to each other in series and which comprises a feedback circuit, (iii) a switch which is connected in parallel with one of said two resistors and is used as a non-continuity when said specific-signal detector detects the specific signal, and (iv) a voltage-controlled oscillator which generates the sampling clock, which has a frequency proportional to that of an outputted voltage of said low-pass filter.   
     
     
       2. An apparatus for reproducing information from an optical information recording medium comprising an area for recording a phase-locked-loop synchronizing signal and an area for recording data, and a specific signal recorded between the two areas, said apparatus comprising: means for generating a reproduction signal by scanning a recording medium with an optical beam;   a specific-signal detector for detecting the specific signal from the reproduction signal;   a binary-conversion circuit for converting the reproduction signal to a binary signal;   a sampling-clock generating circuit for generating a sampling clock synchronized with the binary reproduction signal; and   a reproduction circuit for reproducing information by sampling the binary reproduction signal with the sampling clock,   wherein said sampling-clock generating circuit comprises (i) a phase-comparator which generates a phase-comparing signal by comparing a phase of the binary reproduction signal and that of the sampling clock, (ii) a low-pass filter comprising an amplifier into which the phase-comparing signal is inputted and which comprises a feedback circuit which includes a first condenser and a second condenser, connected in parallel with the first condenser through a switch which is used as a continuity when said specific-signal detector detects the specific signal, and (iii) a voltage-controlled oscillator which generates the sampling clock, which has a frequency proportional to that of a voltage output by said low-pass filter.   
     
     
       3. An optical information reproduction apparatus for reproducing information from an optical information recording medium comprising an area for recording a phase-locked-loop synchronizing signal and an area for recording data, and a specific signal recorded between the two areas, said apparatus comprising: means for generating a reproduction signal by scanning the recording medium with an optical beam;   a specific-signal detector for detecting the specific signal from the reproduction signal;   a binary-conversion circuit for converting the reproduction signal to a binary signal;   a sampling-clock generating circuit for generating a sampling clock synchronized with the binary reproduction signal; and   a reproduction circuit for reproducing information by sampling the reproduction signal with the sampling clock,   wherein said sampling-clock generating circuit comprises (i) a phase-comparator which generates a phase-comparing signal by comparing a phase of the binary reproduction signal with that of the sampling clock, (ii) a low-pass filter which comprises an amplifier into which the phase-comparing signal is inputted and which comprises a feedback circuit which comprises two condensers connected in series to each other, (iii) a switch which is connected in parallel with one of said two condensers and is used as a continuity when said specific-signal detector detects the specific signal, and (iv) a voltage-controlled oscillator which generates the sampling clock, which has a frequency proportional to that of an outputted voltage of said low-pass filter.